A relay wireless transmit/receive unit (WTRU) may provide connectivity to a remote WTRU that may be out of coverage of a network. The relay WTRU may communicate with the remote WTRU via a PC5 interface. Proximity services (ProSe) may enable a direct communication between the relay WTRU and the remote WTRU using, for example, LTE radio interfaces. Unlike communications over a Uu interface between a relay WTRU and an eNodeB, ProSe communications over the PC5 interface between a relay WTRU and a remote WTRU may not support quality of service (QoS). PC5 interface may support ProSe per packet priority. A relay WTRU may need mechanisms to determine a ProSe per packet priority value.